Compliant foil fluid film thrust bearing with a tilting pad underspring

ABSTRACT

A compliant foil fluid film thrust bearing including a thrust disk rotor, fluid foils, spring foils, a thrust plate, and a housing thrust surface The non-rotating but compliant fluid foils, mounted on the thrust plate and/or housing thrust surface and positioned adjacent to the thrust disk, have open faced channels that induce regenerative vortex flow patterns in the process fluid. The multiple spring foils together provide a tilting pad support for the fluid foils but allow them to follow the axial and overturning motion of the thrust disk. The interaction of the tilting pad underspring supports and the circumferential fluid pressure gradients in the process fluid between the fluid foils and the thrust disk rotor assure that the fluid foils will assume hydrodynamically efficient convex shapes on the surfaces adjacent to the rotor regardless of the load applied to the thrust bearing.

TECHNICAL FIELD

This invention relates to the general field of compliant foil fluid filmbearings and more particularly to an improved thrust bearing employingfluid foils and multiple spring foils to support, position, damp andaccommodate movements or excursions of the rotating portion of thebearing.

BACKGROUND OF THE INVENTION

Compliant foil fluid film thrust bearings are currently being utilizedin a variety of high speed rotor applications. These bearings aregenerally comprised of a two sided thrust disk rotating element,non-rotating compliant fluid foil members that axially enclose therotating element, non-rotating compliant spring foil members thataxially enclose the fluid foil members and a non-rotating thrust plateelement and a non-rotating housing element that axially enclose andprovide attachments for the foil members. The space between the rotatingelement and the thrust plate element on one side of the bearing and thespace between the rotating element and the thrust surface of the housingelement on the other side of the bearing are filled with fluid (usuallyair) which envelops the foils.

The rotary motion of the rotating element applies viscous drag forces tothe fluid and induces circumferential flow of the fluid between thesmooth surface of the rotating element and the fluid foil. The spacebetween the rotating element and the fluid foil is subdivided into aplurality of fluid-dynamic wedge channels. These wedge channels havetypically been formed by resistance welding compliant, convex curvedfoil pads to an underlying support foil. The leading ramps of the foilpads relative to the fluid's circumferential flow and the smooth surfaceof the rotating element form the two primary surfaces of the convergingwedge channels. The trailing ramps and the smooth surface of therotating element form the primary surfaces of the diverging wedgechannels. The fluid flowing circumferentially along a converging wedgechannel experiences steadily decreasing flow area, increasingcircumferential flow velocity and increasing static fluid pressure. Ifthe rotating element moves toward the non-rotating element, theconvergence angle of the wedge channel increases causing the fluidpressure rise along the channel to increase. If the rotating elementmoves away, the pressure rise along the wedge channel decreases. Thus,the fluid in the wedge channels exerts restoring forces on the rotatingelement that vary with and stabilize running clearances and preventcontact between the rotating and non-rotating elements of the bearing.Flexing and sliding of the foils causes coulomb damping of any axial oroverturning motion of the rotating element of the bearing.

Owing to preload spring forces or gravity forces, the rotating elementof the bearing is typically in physical contact with the fluid foilmembers of the bearing at low rotational speeds. This physical contactresults in bearing wear. It is only when the rotor speed is above whatis termed the lift-off/touch-down speed that the fluid dynamic forcesgenerated in the wedge channels assure a running gap between therotating and non-rotating elements.

Conventional, compliant foil fluid film thrust bearings have fluiddynamic wedge channel ramps that converge or diverge circumferentiallywith no radial component to the ramp slopes. The converging wedgechannel ramps have no side wall or other constraints to prevent fluidflow out of the channels at their inner and outer edges. At the trailingedge of the converging wedge channel, the high fluid pressure and lackof radial flow constraints induces radial flow leakage out of thechannel, which in turn, results in a reduction in fluid pressure, a lossin bearing load capacity, and an increase in bearing drag. The radialflow leakage requires make-up flow at the beginning of the convergingwedge channel.

Conventional, compliant foil fluid film thrust bearings have primaryfluid flow patterns in the converging wedge channels that are singlepath recirculating loops. The fluid in the converging wedge channelsadjacent to the rotating disk travels circumferentially in the samedirection as the disk's motion (up the ramp) owing to viscous drag. Thefluid in the converging wedge channels adjacent to the non-rotatingfluid foil travels-circumferentially in the direction opposite to thedisk's motion (down the ramp) owing to the circumferential pressuregradient along the channel. Much of the fluid that travels up the rampnear the disk while gaining static pressure turns back before reachingthe end of the wedge channel and travels down the ramp near the fluidfoil while losing pressure. Almost all of this fluid turns again beforereaching the beginning of the wedge channels and travels up the rampwhile again gaining pressure. The fluid traveling the single pathrecirculating loop flow patterns travels essentially the same path eachloop and experiences the same pressure increases and pressure decreaseseach loop with no net pressure gain from one loop to the next. Thesebearings generate less fluid dynamic pressure and have less loadcapacity than bearings that utilize multi-path vortex flow patternswhere the flow traveling each regenerative loop travels a different pathand where there is a net increase in fluid pressure each loop

Conventional, compliant foil fluid film thrust bearings operate withextremely small running clearances and moderate as opposed to low dragand power consumption. The clearances between the non-rotating fluidfoil's converging channel ramp trailing ends and the rotating thrustdisk are typically less than 100 micro-inches when the bearing isheavily loaded at operating conditions. The bearing's drag coefficientis typically more than 0.005 at operating speed as defined by the ratioof the fluid dynamic drag induced shear forces applied to the disk bythe bearing divided by the thrust load carried by the bearing.

Compliant foil fluid film thrust bearings tend to rely on backingsprings to preload the fluid foils against the relatively moveablerotating element (thrust disk) so as to control foil position/nestingand to establish foil dynamic stability. The bearing starting torque(which should ideally be zero) is directly proportional to these preloadforces. These preload forces also significantly increase the disk speedat which the hydrodynamic effects in the wedge channels are strongenough to lift the rotating element of the bearing out of physicalcontact with the non-rotating members of the bearing. These preloadforces and the high lift-off/touch-down speeds result in significantbearing wear each time the disk is started or stopped.

Many conventional, compliant foil fluid film thrust bearings have largesway spaces and loose compliance, i.e. they do not tightly restrict theaxial or overturning motion of the bearing thrust disk, owing to poorcontrol of spring deflection tolerances inherent in the spring designs.

It has been common for compliant foil fluid film thrust bearings toutilize a plurality of coated, convex curved, compliant fluid foil padsthat are welded to a support foil to form the fluid foil member of thebearing. These two piece fluid foil members are typically thicker andhave poorer thickness control than can single piece fluid foil members.Two piece fluid foil members also experience process fluid foilturbulence, increased drag at operating speeds and reduced load capacityowing to the flow discontinuities between the trailing edges of eachfoil pad and the weld attachment edge of the next circumferentiallylocated pad.

Some conventional, compliant foil fluid film thrust bearings utilizespring foil elements that are formed by milling (chemically orotherwise) circumferentially offset recesses in opposing sides of flatfoil stock so as to leave circumferentially offset unmilled ridges onopposing sides of the foil elements. Pressure applied to the offsetridges induces the spring foil element to deflect in a spring-likemanner. Spring foil elements formed in this manner are prone to largevariations in their spring rates due to small variations in millingdepth. This milling process non-symetrically relieves any residualsurface compressive stresses induced by previous foil rolling operationsand thus induces foil warpage.

Other bearings utilize convolute shaped spring foil elements that areformed by pressing annealed Inconel 750X foil blanks between twocontoured plates having matching wavy contours with constant plate toplate spacing and then heat treating the foil blanks at approximately1300 degrees Fahrenheit for approximately 20 hours while they are stillpressed between the contoured plates. Spring foils formed in this mannerare prone to have large variations in undeflected thickness.

In some cases, the fluid foils may be attached to the spring foils bywelding or brazing or various spring foil elements may be welded orbrazed together to form a spring foil member. Those thrust bearings thatutilize welding or brazing to attach one foil element to another aresubject to foil distortions and foil fatigue failures, particularly atthe bond sites.

The sides of the fluid foils that face the rotating element of thebearing can utilize low rubbing friction coatings to minimize bearingwear when disk speed is below the lift-off/touch-down speed. Thesecoatings, however, may have large thickness tolerances that canadversely affect the foil pack thickness tolerance.

The latest development in compliant foil fluid film thrust bearings,described in U.S. Pat. No. 5,529,398 issued Jun. 25, 1996 to Robert W.Bosley entitled “Compliant Foil Hydrodynamic Fluid Film Thrust Bearing”includes a self shimming capability to compensate for variations in foilpack thickness and three (3) spring or support foils beneath the fluidfoil.

SUMMARY OF THE INVENTION

In the present invention, the compliant foil fluid film thrust bearinggenerally comprises a single sided or two sided thrust disk rotor, fluidfoils, spring /s, a thrust plate, a foil retaining housing and a spacerring. The non-rotating but compliant fluid foils are located adjacent tothe thrust face or faces of the rotatable disk. The fluid foils haveopen faced channels that induce regenerative vortex flow patterns in theprocess fluid. The forces applied by the thrust disk to the fluid foilsvary inversely with fluid foil to disk gap and vary proportionally withdisk deflection.

The spring foils provide a tilting pad support for the fluid foils butallow them to follow the axial and overturning motion of the disk. Eachof the types of foils, namely fluid foils and spring foils are attachedto the foil retaining housing by a compliant web structure and pins. Thefoils are formed as thin, flat, annular sheets with integral shim ringsat their periphery and contoured cutout patterns that are unique to eachtype of foil.

As part of the forming process, the fluid foil blank is coated on oneside with a compliant, wear resistant material then stamped with aforming tool to form the fluid flow channels. The thrust plate ispreloaded towards the thrust surface of the foil retaining housing by apreload spring and is held away from the housing by the total thicknessof the foil shim rings and the thickness of the spacer ring. This allowsthe bearing to essentially self shim itself to establish a smallclearance between the fluid foils and the disk that is not affected bynormal variations in foil or foil coating thicknesses.

The bearing has no preload force and has zero starting torque when therotor's axis of rotation is oriented ninety degrees to the force ofgravity. Owing to the vortex flow pattern of the process fluid, thebearing running clearances and load capacities are improved whilelift-off speeds are reduced. In addition, good damping, low runningtorque and small sway space are achieved. This is all accomplished at alow manufacturing cost with a low parts count.

It is, therefore, a principal object of the present invention to providean improved compliant foil fluid film thrust bearing.

It is another object of the present invention to provide such a bearingwith enhanced axial and overturning load carrying capacity.

It is another object of the present invention to provide such a bearingwith both squeeze film and coulomb damping.

It is another object of the present invention to provide such a bearingwith small sway space clearances to tightly restrict bearing and thrustdisk rotor deflections.

It is another object of the present invention to provide such a bearingwith very low operating torque.

It is another object of the present invention to provide such a bearingwith large running clearances between the fluid foil elements and thethrust disk.

It is another object of the present invention to provide such a bearingwith fluid foil members that are not preloaded by spring forces againstthe thrust disk at zero speed.

It is another object of the present invention to provide such a bearingwith zero starting torque when there is no gravity induced preloadforces.

It is another object of the present invention to provide such a bearingwith an extremely low lift-off/touch-down speed which is consistent withzero preload forces.

It is another object of the present invention to provide such a bearingwith very low starting and stopping wear which is consistent with zeropreload forces and a low lift-off/touch-down speed.

It is another object of the present invention to provide such a bearingwith converging wedge channel features (formed on the surface of thefluid foil element) that limit fluid foil losses from the channel at theradial outer and radial inner edges of those channels.

It is another object of the present invention to provide such a bearingwith converging wedge channel ramps formed on the surface of the fluidfoil elements that have compound curve profiles with concave curvaturesradially, flat slopes circumferentially at zero speed and convexcurvatures at operating speed when fluid dynamic and spring forces areapplied to the fluid foil elements. The profiles will form and functionas scoops with radially wide fluid foil inlets, radially narrowingchannel widths along the circumferential fluid foil paths, and roundedcircumferentially trailing edges.

It is another object of the present invention to provide such a bearingwith a fluid foil pattern that reduces fluid pressure losses when theprocess fluid travels “down the ramp”(in a nominally circumferentialdirection that is opposite to the rotation of the thrust disk) adjacentto the fluid foil element.

It is another object of the present invention to provide such a bearingwith a fluid flow pattern that is regenerative with a different flowpath for each regenerative flow loop.

It is another object of the present invention to provide such a bearingwith a vortex flow pattern.

It is another object of the present invention to provide such a bearingwith fluid flow element blanks and spring foil elements that arefabricated by optically masked chemical etch techniques.

It is another object of the present invention to provide such a bearingwith foil elements that are extremely flat owing to the processes usedto roll and heat treat the foil metal and the processes used to form(e.g. etch) the foil blanks and elements.

It is another object of the present invention to provide such a bearingwith foil elements that have tightly held thickness tolerances.

It is another object of the present invention to provide such a bearingwith fluid foil members that are single fluid foil elements, one foreach side of the bearing.

It is another object of the present invention to provide such a bearingwith fluid foil elements that are formed from blanks by pressing steeplysloped joggles to function as diverging wedge channels which allowingthe gradually converging wedge channel ramps to result without plasticdeformation as the straight line connection between the joggles.

It is another object of the present invention to provide such a bearingwith fluid foil elements that are formed from annealed blanks of nickelsteel, such as Inconel 750X, by pressing at room temperature.

It is another object of the present invention to provide such a bearingwith a spring foil member that has local spring rates that vary withradial and circumferential location so as to accommodate variations influid pressure within the converging wedge channel adjacent to the localareas of the spring foil member.

It is another object of the present invention to provide such a bearingwith a tilting pad spring support system that controls the relativesupport forces applied to the underside of the fluid foil at amultiplicity of locations circumferentially along the converging wedgechannel.

It is another object of the present invention to provide such a bearingwith a tilting pad spring support system having circumferentially closerspacing between support/pivot lines moving up the converging ramp fromthe leading edge of the fluid foil to the trailing edge of the fluidfoil.

It is another object of the present invention to provide such a bearingwith a tilting pad spring support system providing increasing supportforces and support spring rates moving up the converging ramp from theleading edge of the fluid foil to the trailing edge of the fluid foil.

It is another object of the present invention to provide such a bearingwith a tilting pad spring support system with radially curvedsupport/pivot lines.

It is another object of the present invention to provide such a bearingwith a tilting pad spring support system that assures retention of areasonably hydrodynamically optimized scoop shape for the fluid foilconverging ramps over a wide range of bearing operating speeds andbearing thrust loads.

It is another object of the present invention to provide such a bearingwith foil elements that are not welded or brazed to form foil memberassemblies.

It is another object of the present invention to provide such a bearingwith pins (rigidly attached to the bearing housing) which position andresist rotation of the foil elements.

It is another object of the present invention to provide such a bearingwith self shimming capability utilizing the resilient mounting andpreload characteristics of the thrust disk, the spacer ring and thefoil's self shimming rings to prevent variations in bearing axial playand sway space due to variations in foil thickness and foil coatingthickness.

It is another object of the present invention to provide such a bearingwith fluid foil elements, spacer ring element, thrust disk element andthrust plate element that can be installed in the thrust bearing quicklyand easily.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus described the present invention in general terms, referencewill now be made to the accompanying drawings in which:

FIG. 1 is a sectional view of a turbomachine having the compliant foilfluid film thrust bearing of the present invention;

FIG. 2 is an enlarged partial view of oval 2 of FIG. 1 illustrating thethrust plate and spacer area of the compliant foil fluid film thrustbearing of the present invention;

FIG. 3 is a plan view of the fluid foil member of the compliant foilfluid film thrust bearing of the present invention;

FIG. 4 is an enlarged sectional view of the fluid foil member of FIG. 4taken along lines 4—4;

FIG. 5 is another enlarged sectional view of the fluid foil member ofFIG. 4 taken along lines 5—5;

FIG. 6 is a plan view of the outer spring foil element of the springfoil member of the compliant foil fluid film thrust bearing of thepresent invention;

FIG. 7 is a plan view of the intermediate outer spring foil element ofthe spring foil member of the compliant foil fluid film thrust bearingof the present invention;

FIG. 8 is a plan view of the middle spring foil element of the springfoil member of the compliant foil fluid film thrust bearing of thepresent invention;

FIG. 9 is a plan view of the intermediate inner spring foil element ofthe spring foil member of the compliant foil fluid film thrust bearingof the present invention;

FIG. 10 is a plan view of the inner spring foil element of the springfoil member of the compliant foil fluid film thrust bearing of thepresent invention;

FIG. 11 is a plan view, partially cut away foil-by-foil, of thecomplaint foil fluid film thrust bearing of the present invention;

FIG. 12 is a sectional view of the unloaded fluid foil member and springfoil member of FIG. 11 taken along line 12—12;

FIG. 13 is a sectional view of the loaded fluid foil member and springfoil member of FIG. 11 taken along line 12—12;

FIG. 14 is a plan view of an alternate compliant foil fluid film thrustbearing of the present invention;

FIG. 15 is a sectional view of the alternate compliant foil fluid foilthrust bearing of FIG. 14 taken along line 15—15; and

FIG. 16 is a partial plan view of the fluid foil member of an anotheralternate compliant foil fluid film thrust bearing of the presentinvention;

FIG. 17 is a partial plan view of the outer spring foil element of thespring foil member used with the fluid foil member of the alternatecompliant foil fluid film thrust bearing of FIG. 16;

FIG. 18 is a partial plan view of the intermediate outer spring foilelement of the spring foil member used with the fluid foil member of thealternate compliant foil fluid film thrust bearing of FIG. 16;

FIG. 19 is a partial plan view of the middle spring foil element of thespring foil member used with the fluid foil member of the alternatecompliant foil fluid film thrust bearing of FIG. 16;

FIG. 20 is a partial plan view of the intermediate inner spring foilelement of the spring foil member used with the fluid foil member of thealternate compliant foil fluid film thrust bearing of FIG. 16; and

FIG. 21 is a partial plan view of the inner spring foil element of thespring foil member used with the fluid foil member of the alternatecompliant foil fluid film thrust bearing of FIG. 16.

DETAILED DESCRIPTION OF THE

PREFERRED EMBODIMENTS A turbomachine utilizing the compliant foil fluidfilm thrust bearing of the present invention is illustrated in FIG. 1.The turbomachine 10 generally includes turbine wheel 12 and compressorwheel 14 at opposite ends of a common shaft or tie bar 16. The thrustand radial bearing rotor 18 is disposed around the tie bar 16 betweenthe turbine wheel 12 and the compressor wheel 14. A journal bearingcartridge 20 in center bearing housing 22 rotatably supports the bearingrotor 18.

The compressor end of the bearing rotor 18 includes a radially extendingthrust disk 24 which extends into a recess 26 in the compressor end ofthe center bearing housing 22. A bearing thrust plate 28 is disposed onthe opposite side of the bearing rotor thrust disk 24. The outerperiphery of the compressor end of the center bearing housing 22 engagesthe compressor housing 30.

As best illustrated in FIG. 2, a thrust bearing spacer 32 is positionedradially outward from the thrust disk 24 of the bearing rotor 18 and ispositioned radially by a plurality of circumferentially spaced pins 34which are fixed in holes 38 in the recess 26 of the center bearinghousing 22 and extend into holes 38 in the thrust bearing plate 28. Athrust bearing fluid foil member 40 and thrust bearing spring foilmember 42 are disposed on either side of the bearing rotor thrust disk24 and thrust bearing spacer 32. On one side, the fluid foil member 40and spring foil member 42 are positioned in the recess 26 of the centerbearing housing 22 and on the other side they are adjacent to thebearing thrust plate 28. The fluid foil member 40 and spring foil member42 are held in position radially and circumferentially by the pins 34which extend from the center bearing housing 22, through holes in onespring foil element 42, through holes in one fluid foil element 40,traverse the bore of the thrust bearing spacer 32, through holes in theopposite side fluid foil element 40, the holes in the opposite sidespring foil member 42 and into holes 38 in the bearing thrust plate 28.The bearing thrust plate 28 is biased towards the center bearing housing22 by a Belleville washer 23 disposed between the lip 25 on the bearingthrust plate 28 and the compressor housing 30.

The thickness of the thrust bearing spacer 32 is several thousandths ofan inch greater than the thickness of the bearing rotor thrust disk 24.Variations in the foil or foil coating thicknesses inherently causecompensating variations in the spacing between the thrust plate 28 andthe housing 22. Thus, variations in bearing sway space and bearingcompliance due to foil thickness tolerances are prevented.

FIGS. 3-5 illustrate a fluid foil member 40 integrally formed from asingle flat disk termed a foil blank. A plurality of individual fluidfoils 41 are formed from a flat sheet of a nickel steel such as Inconel750X by room temperature pressing steeply sloped joggles to function asdiverging wedge channels while allowing the gradually converging wedgechannel ramps to result without plastic deformation as the straight lineconnection between the joggles. The fluid foil members would normally beannealed both during forming and use and may be coated prior to formingthe joggles with any number of a myriad of low friction or frictionreducing coating materials which can protect the metal from abrasionduring starting and stopping, and inadvertent and occasional high speedtouch-downs. The coating would also provide for some embedment ofcontamination particles.

The individual fluid foils 41 (shown as twelve) are generally chevronshaped and connected to an outer self shimming ring 44 by support webs45. Fluid passages or openings 46 are formed between adjacent supportwebs 45. Every fourth fluid passage 46 includes an indexing tab 47. Eachaerodynamic foil 41 has a trailing edge 48 with a rounded trailing pointor nose 49 and a leading edge 50 a generally straight ramped contourfrom the leading edge 50 to the trailing edge 48. The individual fluidfoils 41 have a generally scoop shape as best illustrated in the twosectional views of FIGS. 4 and 5. One or two rows of openings 51 areprovided at the leading edge 50 of each individual fluid foil 41 toallow fluid to enter the leading edge of the converging ramp adjacent tothe thrust disk from under the fluid foil in the area of the spring foilmembers 42.

As illustrated in FIGS. 6-10, the thrust bearing spring foil member 42generally comprises an outer spring foil element 53 (FIG. 6), anintermediate outer spring foil element 54 (FIG. 7), a middle spring foilelement 55 (FIG. 8), an intermediate inner spring foil element 56 (FIG.9), and an inner spring foil element 57 (FIG. 10).

The outer support foil element 53, shown in FIG. 6, generally includesan inner connector ring 60 and an outer self shimming ring 61 with aplurality (shown as twelve) of narrow width spring foils 62 extendingtherebetween. The narrow spring foils 62 consist of an inner curved foilsection 63 extending outward from the inner connector ring 60 at aforward angle (in the direction of the thrust disk's rotary motion) andan outer curved foil section 64 extending inward from the self shimmingring 61 at a forward angle. The inner and outer foil sections 63,64 arenominally oriented approximately forty degrees from circumferential atall points along their length and join together to form a generallynose-shaped foil section 65. The outer foil sections 64 are individuallyconnected to the outer self shimming ring 61 by a radially extendingconnector or supporting web 66.

The narrow spring foil 53 is narrowest at the connection to the innerconnector ring 60 and gradually increases in width to the point or tipof the nose 65 and continues to gradually increase in width in the outerfoil section 64 to the connector web 66. The connector web 66 is of aneven greater, generally radially increasing, width. A plurality ofindexing tabs 67 (shown as four) extend inward from the outer selfshimming ring 61 in order to enable precise alignment of the outersupport foil element 53 with the other elements of the thrust bearingspring foil member 42 and with the fluid foil member 40.

The intermediate outer support foil element 54, shown in FIG. 7,generally includes an inner connector ring 73 and an outer self shimmingring 72 with a plurality (shown as twelve) of wide spring pads or foils71 extending therebetween. The wide spring foils 71 consist of an innercurved foil section 75 extending outward from the inner connector ring73 at a forward angle and an outer curved foil section 76 extendinginward from the self shimming ring 72 at a forward angle. The inner andouter foil sections 75, 76 join together to form a generally nose-shapedfoil section 77. Each of the outer foil sections 76 are individuallyconnected to the outer self shimming ring 72 by a pair of radiallyextending connector or supporting webs 74. A plurality of concentricouter dam rings 78 (shown as three) extend between the adjacent widespring foils 71 generally where the wide spring foils 71 and the pair ofwebs 74 connect.

The wide spring foil 71 is narrowest at the connection to the innerconnector ring 73 and gradually increases in width to the point or tipof the nose 77 and continues to gradually increase in width in the outerfoil section 76 to the connector webs 74. A plurality of indexing tabs79 (shown as four) extend inward from the outer self shimming ring 72 inorder to enable precise alignment of the outer support foil element 54with the other elements of the thrust bearing spring foil member 42 andwith the fluid foil member 40.

The middle spring foil element 55 is illustrated in FIG. 8 and includesan outer self shimming ring 81 and indexing tabs 82 identical to andaligned with the corresponding elements in the outer spring foil element53, intermediate outer spring foil element 54 and fluid foil member 40.A plurality of pairs (shown as twelve) of generally nose-shaped narrowspring foils 83 extend between the inner connector ring 84 and the outerself shimming ring 81. Each of the pair of narrow spring foils 83generally straddle the narrow spring foils 62 of the outer spring foilelement 53 and are aligned at the leading and trailing edges of the widespring foil 71.

A connector web 87 joins each of the narrow spring foils 83 to the outerself shimming ring 81. A plurality of concentric outer dam rings 85(shown as two) extend between adjacent pairs of narrow spring foils 83where they connect to webs 87. A plurality of concentric inner dam rings86 (shown as three) extend between adjacent pairs of narrow spring foils83 near the inner connector ring 84.

FIG. 9 illustrates the intermediate inner spring foil element 56 whichhas an outer self shimming ring 89 and indexing tabs 91 which are commonto the spring foil member 42. The plurality of pairs of intermediatewidth spring foil elements 92 (shown as twelve) are disposed between theouter self shimming ring 89 and an inner connector ring 90. Each of saidpair of intermediate width spring foil elements are connected to theouter self shimming ring by a pair of webs 94. By intermediate width ismeant a width between the width of the narrow width outer and innerfoils 62, 83 and the width of the wide intermediate outer foil 71.

Each of the pairs of webs 94 for the intermediate width foils are joinedby a circumferential stiffening ring 93. In addition, a single outer damring 96 (which could alternately be a plurality of dam rings) and aplurality (shown as two) of concentric inner dam rings 95 extend betweenadjacent pairs of intermediate width foils 92, at the connection to thewebs 94 and adjacent to the inner connector ring 90, respectively. Eachof the pair of intermediate width foils 92 generally are positioned overone of said pair of narrow width spring foils 83 of the middle springfoil member 55.

The inner spring foil element 57 is illustrated in FIG. 10 and includesan outer self shimming ring 100 and indexing tabs 101 identical to andaligned with the corresponding elements in the other spring foilelements 53, 54, 55, and 56 and fluid foil member 40. A plurality oftrios (shown as twelve) of generally nose-shaped narrow spring foils 102extend between the inner connector ring 103 and the outer self shimmingring 100. Each of the trio of narrow spring foils 102 have widths thatare generally the same as the narrow spring foils 62 of the outer springfoil element 53 and the pairs of narrow spring foils 83 of the middlespring foil element 55. Of the trio of narrow spring foils 102, two arealigned at the leading and trailing edges of one of the pair ofintermediate width spring foils 92 and the third of the trio of narrowspring foils are aligned with the trailing edge of the other of the pairof intermediate width spring foils 92.

A connector web 105 joins each of the trio of narrow spring foils 102 tothe outer self shimming ring 100. These webs 105 of each trio of narrowspring foils 102 are joined together by a circumferential stiffeningring 106.

The precise relationship of the fluid foil member 40 and spring foilmember 42, including the five spring foil elements 53, 54, 55, 56 & 57,is best illustrated in FIGS. 11-13. FIG. 11 is a plan view of theassembled fluid foil member 40 and spring foil member 42 with theindividual spring foil elements overlain and positioned by theirrespective indexing tabs. Proceeding in a counterclockwise rotation, theindividual spring foil elements are individually cut away in afoil-by-foil manner to show their relationship with each other.

The outer spring foil 62 is shown in the arc identified as “A”. Arc “B”illustrates the outer intermediate foil 71 aligned over the outer springfoil 62. A pair of middle spring foils 83 are laid over the outer springfoil 62 and intermediate spring foil 71 in arc “C”. Arc “D” thenincludes the pair of intermediate inner foils 92 and finally the trio ofinner foils 102 are shown over the pair of intermediate inner foils 92in arc “E”. The fluid foils 41 are then laid over the assembled springfoils in arc “F”.

An even more precise relationship of the various foils is illustrated inFIGS. 12 and 13. FIG. 12 illustrates an unloaded fluid foil member andspring foil member while a loaded fluid foil member and spring foilmember are shown in FIG. 11. It should be noted that the foil 62 islocated nearer to the trailing edge of foil 71 than to the leading edgeof foil 71. Foils 83 are located nearer the trailing edge of foils 92than to the leading edge of foils 92. This assures that the tilting padspring support will deliver more force to the underside of the fluidfoil 40 near its trailing edge 48 than its leading edge 50.

The fluid foil blank, as well as the individual elements of the thrustbearing spring foil member 42, can be formed from flat metal sheets byoptically masked chemical etch techniques. Nickel steels, such asInconel 750X for the fluid foil and Inconel 718 for the spring foilelements can be used. Typically, foil thicknesses are between 0.004inches and 0.007 inches. The nickel steel metal sheets from which thefoil elements are formed normally are heat treated to full hardness in avacuum oven (1300 degrees Fahrenheit for about twenty hours for Inconel750X). The five individual elements of the thrust bearing spring foilmember 42 can be assembled by stacking the spring foil elements withoutbonding. The relative micro movement of these foils in use providescoulomb damping.

The shape of the fluid foils 41, namely an open-faced channel having aconverging width and sloping “walls”, induces regenerative vortex flowpatterns in the process fluid across the fluid foil. The process fluidgenerally enters the leading surface of the foil 41 from the trailingedge 48 of the preceding foil. Any make-up process fluid is providedfrom the inner and outer diameter of the leading edge or from openings51. There is some fluid leakage flow from the inner diameter and outerdiameter, respectively, near the trailing edge 48.

The compliant fluid foil members 40 are located adjacent to the twothrust faces of the thrust disk 24. The spring foil members 42 providesupport for the fluid foil members 40 but allow them to follow the axialand overturning motion of the disk 24. The forces applied by the fluidfoil members to the thrust disk through the process fluid vary inverselywith foil to disk gap and vary proportionally with disk deflection.

The thrust plate 28 is held away from the center bearing housing 22 bythe total thickness of the outer self shimming rings of the fluid foilmembers 40 and spring foil members 42 and the thickness of the thrustbearing spacer 32. The thrust bearing spacer 32 is slightly thicker thanthe thrust disk 24 so that there is a small clearance between the fluidfoil member 40 and the thrust disk 24 that is not affected by normalvariations in foil or foil coating thickness. The bearing has no preloadforce and has zero starting torque when the disk's axis of rotation isoriented ninety degrees to the force of gravity. With the regenerativevortex flow pattern established by the contour of the fluid foilelements, the bearing running clearances are significantly improved(increased) and lift-off speeds are significantly less than previouslypossible.

The converging wedge channel ramps formed in the surface of the fluidfoil members have compound curve profiles with concave curvaturesradially, flat slopes circumferentially at zero speed and convexcurvatures at operating speed when fluid dynamic and spring forces areapplied to the foil elements. The tilting pad support for the fluid foilelements assures a near optimum convex curvature circumferentially overa wide range of bearing thrust loads. The profiles will form andfunction as scoops with radially wide fluid flow inlets, a radiallynarrowing channel width along the circumferential fluid foil paths, androunded circumferentially trailing edges. This multi-path regenerativevortex fluid foil pattern reduces fluid pressure losses when the processfluid travels “down the ramp” in a nominally circumferential directionthat is opposite to the rotation of the thrust disk adjacent to thefluid foil member.

The particular tilting pad bearing of the present invention has fivespring foils and a fluid foil. The five spring foil elements have foursupport lines for each fluid foil ramp. The relative force exerted ateach of these support lines is proportionally controlled by thecircumferential spacing between several curved spring foil lines thatgenerally match the curved shape of the formed fluid foil.

The outer spring foil element 53 has twelve individual narrow widthspring foils 62 adjacent to either the thrust disk on one side of thethrust bearing or to the thrust surface of the housing on the other sideof the thrust disk. Each of these narrow spring foils 62 provides acurved, generally nose shaped support line.

The wide intermediate outer spring foils 71 are supported by theindividual narrow spring foils 62 and can articulate both by flexing andby tilting on the single support line of the narrow spring foils 62 toeither a nose up or nose down position as required by the rest of thethrust bearing.

Above the wide spring foils 71 are the pair of narrow width spring foils83 which provide two support lines per ramp and can give support at thenose and the leading edge of the wide spring foils 71. The two foilsupport lines of narrow spring foils 83 push underneath and near theperipheral center of each of the two pairs of intermediate width foils92 so that these intermediate width foils 92 can tilt nose up or nosedown as required. Lastly, narrow width spring foils 102 have threesupport lines, one at the trailing edge of the leading spring foil 92,one at the leading edge of the trailing spring foil 92 and one at thetrailing edge of the trailing spring foil 92.

Effectively, intermediate width foil 92 provide a line of supportpushing on the underside of the fluid foil relatively close to the startof the converging ramp, and then the next three support lines moving upthe ramp are provided to the fluid foil through spring foil 102. Thismakes the entire spring structure behave like the articulated supportsof tank treads, where as you go over uneven ground the tank treadsthemselves can articulate because you have a support structure thatarticulates. The circumferential spacing between these various supportlines, now referring to the support lines of spring foil elements 53,55, 56, and 57, control the percentage of the total force coming throughthe spring foil elements which is delivered to each circumferentiallocation on the fluid foil above the spring foil element 57.

The highest spring force will be at the nose of the formed fluid foilwhere the fluid compressed pressure is highest. The support forces andthe spring rates produced are lower when moving away from the springfoil nose. While these foil elements are primarily tilting members toallow compliance to the fluid foil, they also have spring properties intheir own right.

The concentric dam rings of spring foil elements 54, 55, and 56effectively serve as dams to limit leakage out of the thrust bearingparticularly when the bearing is operated hydrostatically. The thrustbearing of the present invention is particularly useful in ahydrostatically augmented thrust bearing such as described in U.S.patent application Ser. No. 08/622,250 filed Jun. 14, 1996 by Robert W.Bosley and Ronald F. Miller entitled “Hydrostatic Augmentation of aCompliant Foil Hydrodynamic Fluid Film Thrust Bearing”, incorporatedherein by reference. The openings 51 at the leading edge of the fluidfoil 41 are specifically provided for this hydrostatic augmentation. Thethrust bearing will, however, function as a hydrodynamic thrust bearingwith or without openings 51.

The tilting pad thrust bearing operates with its fluid foil flexedcircumferentially in a convex fluid dynamically optimized shape on thesurface adjacent to the thrust disk without relying upon air pressure inthe spring area. Air pressure will, however, provide additional convexshaping and load capacity and provide good adaptability.

While the nose shape of the individual spring foils has been shown to berelatively identical for the five spring foils and the fluid foil, theshape of the spring foil nose can be varied to control the spring rate.As illustrated in FIGS. 14 and 15, the nose of the trailing edge ofmiddle spring foil 83′ can be sharper, that is have a smaller radiusthan the noses of the trailing edge of inner spring foil 102 andintermediate inner spring foil 92. This will stiffen up the spring rateat the end of the converging ramp so that there will be less fluid flowleakage and provide greater support for the fluid foil nose.

The generally scoop-shaped converging wedge channels formed on thesurface of the fluid foil members induce vortex fluid foil patterns andlimit process fluid foil losses from the channels at the radial innerand outer edges of the foils. This, together with the self shimmingconstruction and other features of the present invention, provides athrust bearing having a high load carrying capacity, good damping, smallsway clearances, low running torque, high running foil to diskclearances, zero preload force, low starting torque, lowlift-off/touch-down speeds, and low wear. In addition, all of this isachieved with a low parts count, low manufacturing cost, and ease ofassembly.

Further, the fluid foil members and spring foil elements can have astraight radial shape as shown in FIGS. 16-21. Except for having astraight radial shape rather than the nose shape previously described,the fluid foil member 40′ having straight radial foils 141 and spring orsupport foil members 53′, 54′, 55′, 56′, and 57′ would functiongenerally the same and have the same relative spacing and relativepositioning with respect to each other. The outer support foil element53′ of FIG. 17 includes narrow width radial spring foils 162,intermediate outer support foil element 54′ of FIG. 18 includes wideradial pads or foils 171, middle support foil element 55′ of FIG. 19includes pairs of narrow width radial spring foils 183, intermediateinner support foil element 56′ of FIG. 20 includes pairs of wide radialspring pads or foils 192, while inner support foil element 57′ of FIG.21 includes trios of narrow width radial spring foils 202. The generallyflat (radially) fluid foil surfaces, and underlying spring foils whichmaintain generally flat (radially) fluid foil surfaces of FIGS. 16-21,are not intended to establish a scoop shaped converging ramp andtherefor do not generate vortex regenerative process fluid flows.

While specific embodiments of the invention have been illustrated anddescribed, it is to be understood that these are provided by way ofexample only and that the invention is not to be construed as beinglimited thereto but only by the proper scope of the following claims.

What I claim is:
 1. A method of rotatably supporting a thrust disk on athrust plate comprising the steps of: providing a compliant foil bearingbetween said thrust disk and said thrust plate, said compliant foilbearing including an annular compliant fluid foil member having aplurality of converging ramps and diverging joggles to form alternatingconverging and diverging wedge channels on the surface of said annularcompliant fluid foil member facing said thrust disk; mounting a springfoil member between said compliant fluid foil bearing member and saidthrust plate; providing said spring foil member with a plurality ofspring foil elements having a number of narrow width spring foils and aplurality of spring foil elements having a number of wide spring pads;and creating a tilting pad support for said compliant fluid foil bearingmember by alternating individual ones of said plurality of said narrowwidth spring foil elements and individual ones of said plurality of widespring pad spring foil elements.
 2. A compliant foil fluid film thrustbearing comprising: a thrust disk rotatably supported by a non-rotatingthrust bearing surface; and a compliant foil bearing operably disposedbetween said rotatable thrust disk and said non-rotating thrust bearingsurface and mounted on said thrust bearing surface, said compliant foilbearing including a fluid film member having a plurality of convergingramps and diverging joggles to form alternating converging and divergingwedge channels on the surface of said compliant fluid foil member facingsaid rotatable thrust disk, and a spring foil member mounted on saidthrust bearing surface and disposed between said thrust bearing surfaceand said fluid foil member, said spring foil member including means toform a tilting pad support for said fluid foil member.
 3. The compliantfoil fluid film bearing of claim 2 wherein said means to form a tiltingpad support for said fluid foil member has circumferentially closerspacing between support/pivot lines moving up the individual convergingramps of said fluid foil member to the trailing edge of the individualconverging ramps of said fluid foil member.
 4. The compliant foil fluidfilm bearing of claim 3 wherein said support/pivot lines moving up theindividual converging ramps of said fluid foil member to the trailingedge of the individual converging ramps of said fluid foil member numberthree.
 5. The compliant foil fluid film bearing of claim 3 wherein saidsupport/pivot lines moving up the individual converging ramps of saidfluid foil member to the trailing edge of the individual convergingramps of said fluid foil member number four.
 6. The compliant foil fluidfilm bearing of claim 2 wherein said means to form a tilting pad supportfor said fluid foil member has increasing support forces and supportspring rates moving up the individual converging ramps of said fluidfoil member to the trailing edge of the individual converging ramps ofsaid fluid foil member.
 7. The compliant foil fluid film bearing ofclaim 2 wherein said means to form a tilting pad support for said fluidfoil member assures retention of a reasonably hydrodynamically optimizedscoop shape for the individual converging ramps of said fluid foilmember over a wide range of bearing operating speeds and bearing thrustloads.
 8. A compliant foil fluid film thrust bearing comprising: athrust disk rotatably supported by said thrust bearing surface; and acompliant foil bearing operably disposed between said rotatable thrustdisk and said thrust bearing surface and mounted on said thrust bearingsurface, said compliant foil bearing including a fluid foil memberhaving a plurality of converging ramps and diverging joggles to formalternating converging and diverging wedge channels on the surface ofsaid compliant fluid foil member facing said rotatable thrust disk, anda spring foil member mounted on said thrust bearing surface and disposedbetween said thrust bearing surface and said fluid foil member, saidspring foil member including means to provide narrow pivot supports andto provide flexure and tilting supports for said fluid foil member. 9.The compliant foil fluid film bearing of claim 8 wherein said narrowpivot supports are radially curved.
 10. The compliant foil fluid filmbearing of claim 9 wherein said narrow pivot supports have a generallychevron shape with a generally blunt nose.
 11. The compliant foil fluidfilm bearing of claim 8 wherein said narrow pivot supports are radiallystraight.
 12. A compliant foil fluid film thrust bearing comprising: athrust disk rotatably supported by said thrust bearing surface; and acompliant foil bearing operably disposed between said rotatable thrustdisk and said thrust bearing surface and mounted on said thrust bearingsurface, said compliant foil bearing including a fluid foil memberhaving a plurality of converging ramps and diverging wedge channels onthe surface of said compliant fluid foil member facing said rotatablethrust disk, and a spring foil member mounted on said thrust bearingsurface and disposed between said thrust bearing surface and said fluidfoil member, said spring foil member including a plurality of narrowwidth spring foil elements and at least one wide spring pad element withsaid wide spring elements disposed between adjacent narrow width springfoil elements to form a tilting pad support for said fluid foil member.13. The compliant foil fluid film bearing of claim 12A compliant foilfluid film thrust bearing comprising: a thrust disk rotatably supportedby said thrust bearing surface; and a compliant foil bearing operablydisposed between said rotatable thrust disk and said thrust bearingsurface and mounted on said thrust bearing surface, said compliant foilbearing including a fluid film member having a plurality of convergingramps and diverging joggles to form alternating converging and divergingwedge channels on the surface of said compliant fluid foil member facingsaid rotatable thrust disk, and a spring foil member mounted on saidthrust bearing surface and disposed between said thrust bearing surfaceand said fluid foil member, said spring foil member including aplurality of narrow width spring foil elements and at least one widespring pad element with said wide spring elements disposed betweenadjacent narrow width spring foil elements to form a tilting pad supportfor said fluid foil member, wherein said spring foil member includesthree narrow width spring foil elements and two wide spring padelements.
 14. A compliant foil fluid film thrust bearing comprising: athrust disk rotatably supported by said thrust bearing surface; and acompliant foil bearing operably disposed between said rotatable thrustdisk and said thrust bearing surface and mounted on said thrust bearingsurface, said compliant foil bearing including a fluid foil memberhaving a plurality of converging ramps and diverging joggles to formalternating converging and diverging wedge channels on the surface ofsaid compliant fluid foil member facing said rotatable thrust disk, anda spring foil member mounted on said thrust bearing surface and disposedbetween said thrust bearing surface and said fluid foil member, saidspring foil member including means to provide single narrow pivotsupports and single flexure and tilting supports for said fluid foilmember, pairs of pivot supports and pairs of flexure and titlingsupports, and trios of narrow pivot supports, said single narrow pivotsupports, single flexure and tilting supports, pairs of pivot supports,pairs of flexure and titling supports, and trios of narrow pivotsupports sequentially arranged together to form a tilting pad supportfor said fluid foil member.
 15. A compliant foil fluid film thrustbearing comprising: a bearing housing having a thrust bearing surfaceand a generally opposed thrust bearing plate; a shaft rotatablysupported within said bearing housing and including a thrust diskradially extending between said thrust bearing surface and said opposedthrust bearing plate; a pair of annular compliant fluid foil memberswith one of said pair of members disposed on either side of said thrustdisk and each of said pair of annular compliant fluid foil membersincluding a plurality of converging ramps and diverging joggles to formalternating converging and diverging wedge channels on the surfacefacing said thrust disk; a pair of annular spring foil members with oneof said pair of members disposed between an annular compliant fluid foilmember and said thrust bearing surface and the other of said pair ofannular spring foil members disposed between said other of said pair ofannular compliant fluid foil members and said thrust bearing plate andeach of said annular spring foil members including means to form atilting pad support for said fluid foil member.
 16. The compliant foilfluid film bearing of claim 15 wherein the periphery of each of saidpair of annular compliant fluid foil members includes a self-shimmingperipheral ring and the periphery of each of said pair of annular springfoil members includes a self-shimming peripheral ring: in addition abearing spacer disposed between said pair of annular compliant fluidfoil members at the outer periphery of said thrust disk and said bearingspacer having an axial thickness slightly greater than the axialthickness of said thrust disk such that the thickness of said pair ofannular compliant fluid foil member peripheral rings, the thickness ofsaid pair of annular spring foil member peripheral rings and thethickness of said bearing spacer together establishing a clearancebetween the annular compliant fluid foil elements and said rotatingthrust disk; and wherein each of said pair of annular compliant fluidfoil members and each of said pair of annular spring foil membersinclude a plurality of peripheral tabs having indexing openings thereinand, in addition, said bearing includes a like plurality of pins withindividual pins extending from said bearing housing through said annularcompliant fluid foil members, said annular spring foil members, saidbearing spacer and into said thrust bearing plate.
 17. The compliantfoil fluid film thrust bearing of claim 15 wherein said pair of annularspring foil members includes spring foil elements which have arcuatedams at the radially outward and radially inward periphery of saidtilting pad supports.
 18. The compliant foil fluid film thrust bearingof claim 15 wherein said converging wedge channels are generally scoopshaped chevrons.
 19. The compliant foil fluid film thrust bearing ofclaim 18 wherein said spring foil members includes a plurality of narrowwidth spring foil elements and at least one wide spring pad element withsaid wide spring elements disposed between adjacent narrow width springfoil elements to form a tilting pad support for said fluid foil member.20. The compliant foil fluid film thrust bearing of claim 18 whereinsaid spring foil members include means to provide single narrow pivotsupports and single flexure and tilting supports for said fluid foilmember, pairs of pivot supports and pairs of flexure and titlingsupports, and trios of narrow pivot supports, said single narrow pivotsupports, single flexure and tilting supports, pairs of pivot supports,pairs of flexure and titling supports, and trios of narrow pivotsupports sequentially arranged together to form a tilting pad supportfor said fluid foil member.
 21. The compliant foil fluid film thrustbearing of claim 18 wherein said spring foil members include: aplurality of first narrow pivot supports; a plurality of first wideflexure and tilting support pads having a trailing edge and a leadingedge, with a first narrow pivot support pivotably supporting a firstwide support pad intermediate the trailing edge and the leading edge ofsaid first wide flexure and tilting support pad; a plurality of pairs ofsecond narrow pivot supports, with the trailing of a pair of secondnarrow pivot supports disposed on the trailing edge of a first wideflexure and tilting support pad and the leading of said pair of secondnarrow pivot supports disposed on the leading edge of a first wideflexure and tilting support pad; a plurality of pairs of second wideflexure and tilting support pads each having a trailing edge and aleading edge, with the trailing of a pair of second narrow pivotsupports pivotably supporting the trailing of a pair of second wideflexure and tilting support pads intermediate the trailing edge and theleading edge of said second wide flexure and tilting support pad and theleading of said pair of second narrow pivot supports pivotablysupporting the leading of said pair of second wide flexure and tiltingsupport pads intermediate the trailing edge and the leading edge of saidsecond wide flexure and tilting support pad; and a plurality of trios ofthird narrow pivot supports, with one of a trio of third narrow pivotsupports disposed on the trailing edge of the trailing of said pair ofsecond wide flexure and tilting support pads, one of said trio of thirdnarrow pivot supports disposed on the leading edge of by trailing ofsaid pair of second wide flexure and tilting support pads, and one ofsaid trio of third narrow pivot supports disposed on the trailing edgeof the leading of said pair of second wide flexure and tilting supportpads, each of said generally scoop shaped chevrons supported by a trioof third narrow pivot supports and the leading edge of the leading ofsaid pair of second wide flexure and tilting support pads.
 22. Thecompliant foil fluid film thrust bearing of claim 21 wherein said firstnarrow pivot support pivotably supports said first wide flexure andtilting support pad closer to the trailing edge of said first wideflexure and tilting support pad than to the leading edge of said firstwide flexure and tilting support pad, the trailing of a pair of secondnarrow pivot supports pivotably supports the trailing of a pair ofsecond wide flexure and tilting support pads closer to trailing edge ofsaid second wide flexure and tilting support pad than to the leadingedge of said second wide flexure and tilting support pad, and theleading of said pair of second narrow pivot supports pivotably supportsthe leading of said pair of second wide flexure and tilting support padscloser to trailing edge of said second wide flexure and tilting supportpad than to the leading edge of said second wide flexure and tiltingsupport pad.
 23. The compliant foil fluid film thrust bearing of claim21 wherein said first narrow pivot support pivotably supports said firstwide flexure and tilting support pad closer to the trailing edge of saidfirst wide flexure and tilting support pad than to the leading edge ofsaid first wide flexure and tilting support pad, the trailing of a pairof second narrow pivot supports pivotably supports the trailing of apair of second wide flexure and tilting support pads closer to trailingedge of said second wide flexure and tilting support pad than to thecenter said second wide flexure and tilting support pad, and the leadingof said pair of second narrow pivot supports pivotably supports theleading of said pair of second wide flexure and tilting support padscloser to trailing edge of said second wide flexure and tilting supportpad than to the center of said second wide flexure and tilting supportpad.
 24. The compliant foil fluid film thrust bearing of claim 15wherein said converging wedge channels are generally annular segmentshaving a radial leading edge and a radial trailing edge.
 25. Thecompliant foil fluid film thrust bearing of claim 24 wherein said springfoil members include means to provide single narrow pivot supports andsingle flexure and tilting supports for said fluid foil member, pairs ofpivot supports and pairs of flexure and titling supports, and trios ofnarrow pivot supports, said single narrow pivot supports, single flexureand tilting supports, pairs of pivot supports, pairs of flexure andtitling supports, and trios of narrow pivot supports sequentiallyarranged together to form a tilting pad support for said fluid foilmember.
 26. The compliant foil fluid film thrust bearing of claim 24wherein said spring foil members include: a plurality of first narrowpivot supports; a plurality of first wide flexure and tilting supportpads having a trailing edge and a leading edge, with a first narrowpivot support pivotably supporting a first wide support pad intermediatethe trailing edge and the leading edge of said first wide flexure andtilting support pad; a plurality of pairs of second narrow pivotsupports, with the trailing of a pair of second narrow pivot supportsdisposed on the trailing edge of a first wide flexure and tiltingsupport pad and the leading of said pair of second narrow pivot supportsdisposed on the leading edge of a first wide flexure and tilting supportpad; a plurality of pairs of second wide flexure and tilting supportpads each having a trailing edge and a leading edge, with the trailingof a pair of second narrow pivot supports pivotably supporting thetrailing of a pair of second wide flexure and tilting support padsintermediate the trailing edge and the leading edge of said second wideflexure and tilting support pad and the leading of said pair of secondnarrow pivot supports pivotably supporting the leading of said pair ofsecond wide flexure and tilting support pads intermediate the trailingedge and the leading edge of said second wide flexure and tiltingsupport pad; and a plurality of trios of third narrow pivot supports,with one of a trio of third narrow pivot supports disposed on thetrailing edge of the trailing of said pair of second wide flexure andtilting support pads, one of said trio of third narrow pivot supportsdisposed on the leading edge of the trailing of said pair of second wideflexure and tilting support pads, and one of said trio of third narrowpivot supports disposed on the trailing edge of the leading of said pairof second wide flexure and tilting support pads, each of said radiallysided annular segments supported by a trio of third narrow pivotsupports and the leading edge of the leading of said pair of second wideflexure and tilting support pads.
 27. The compliant foil fluid filmthrust bearing of claim 26 wherein said first narrow pivot supportpivotably supports said first wide flexure and tilting support padcloser to the trailing edge of said first wide flexure and tiltingsupport pad than to the leading edge of said first wide flexure andtilting support pad, the trailing of a pair of second narrow pivotsupports pivotably supports the trailing of a pair of second wideflexure and tilting support pads closer to trailing edge of said secondwide flexure and tilting support pad than to the leading edge of saidsecond wide flexure and tilting support pad, and the leading of saidpair of second narrow pivot supports pivotably supports the leading ofsaid pair of second wide flexure and tilting support pads closer totrailing edge of said second wide flexure and tilting support pad thanto the leading edge of said second wide flexure and tilting support pad.28. The compliant foil fluid film thrust bearing of claim 26 whereinsaid first narrow pivot support pivotably supports said first wideflexure and tilting support pad closer to the trailing edge of saidfirst wide flexure and tilting support pad than to the leading edge ofsaid first wide flexure and tilting support pad, the trailing of a pairof second narrow pivot supports pivotably supports the trailing of apair of second wide flexure and tilting support pads closer to trailingedge of said second wide flexure and tilting support pad than to thecenter said center wide flexure and tilting support pad, and the leadingof said pair of second narrow pivot supports pivotably supports theleading of said pair of second wide flexure and tilting support padscloser to trailing edge of said second wide flexure and tilting supportpad than to the center of said second wide flexure and tilting supportpad.
 29. The compliant foil fluid film thrust bearing of claim 24wherein said spring foil members includes a plurality of narrow widthspring foil elements and at least one wide spring pad element with saidwide spring elements disposed between adjacent narrow width spring foilelements to form a tilting pad support for said fluid foil member.
 30. Acompliant foil thrust bearing comprising: an aerofoil disk having aplurality of fluid foils; and a spring assembly providing flex and tiltsupport to the plurality of fluid foils comprising at least oneindependent flex and tilt support.
 31. The thrust bearing of claim 30wherein the aerofoil disk further comprises: a shim ring having an innerdiameter; a plurality of fluid foils formed on an annular ringconcentric with the shim ring and having a smaller diameter than theshim ring inner diameter; a plurality of web elements, each web elementconnecting the shim ring and the plurality of fluid foils.
 32. Thethrust bearing of claim 30 wherein the spring assembly furthercomprises: means for supporting each of the plurality of fluid foils;first means for providing flex and tilt support for the means forsupporting each of the plurality of fluid foils; first means forproviding pivotal support for the first means for providing flex andtilt support; second means for providing flex and tilt support for thefirst means for providing pivotal support; and second means forproviding pivotal support for the second means for providing flex andtilt support.
 33. The thrust bearing of claim 30 wherein the springassembly further comprises: a plurality of spring foils disks.
 34. Thethrust bearing of claim 33 wherein each of the plurality of spring foildisks further comprises: a shim ring having an inner diameter; aplurality of support elements formed concentric with the shim ring andwithin the shim ring inner diameter; a plurality of web elements, eachweb element connecting the shim ring and one of the plurality of supportelements.
 35. The thrust bearing of claim 30 wherein the spring assemblyfurther comprises: a plurality of foil supports; a plurality of firstflex and tilt supports, each first flex and tilt support supporting oneor two of the plurality of foil supports; a plurality of first pivotsupports, each first pivot support supporting one of the plurality offirst flex and tilt supports; a plurality of second flex and tiltsupports, each second flex and tilt support supporting two of theplurality of first pivot supports; and a plurality of second pivotsupports, each second pivot support supporting one of the plurality ofsecond flex and tilt supports.
 36. The thrust bearing of claim 35wherein: the plurality of foil supports are generally radial; theplurality of first pivot supports are generally radial; and theplurality of second pivot supports are generally radial.
 37. The thrustbearing of claim 30 wherein said bearing is hydrodynamic.
 38. The thrustbearing of claim 30 wherein said bearing is hydrostatic.
 39. A compliantfoil thrust bearing comprising: a fluid foil member having a pluralityof fluid foils; a spring assembly providing flex and tilt support to theplurality of fluid foils comprising at least one independent flex andtilt support.
 40. The thrust bearding of claim 39 wherein the fluid foilmember further comprises: a shim ring having an inner diameter; aplurality of fluid foils formed on an annular ring concentric with theshim ring and having a smaller diameter than the shim ring innerdiameter; a plurality of web elements, each web element connecting theshim ring and the plurality of fluid foils.
 41. The thrust bearing ofclaim 39 wherein the spring assembly further comprises: means forsupporting each of the plurality of fluid foils; first means forproviding flex and tilt support for the means for supporting each of theplurality of fluid foils; first means for providing pivotal support forthe first means for providing flex and tilt support; second means forproviding flex and tilt support for the first means for providingpivotal support; and second means for providing pivotal support for thesecond means for providing flex and tilt support.
 42. The thrustbearding of claim 39 wherein the spring assembly further comprises: aplurality of spring foil disks.
 43. The thrust bearding of claim 42wherein each of the plurality of spring foil disks further comprises: ashim ring having an inner diameter; a plurality of support elementsformed concentric with the shim ring and within the shim ring innerdiameter; a plurality of web elements, each web element connecting theshim ring and one of the plurality of support elements.
 44. The thrustbearing of claim 39 wherein the spring assembly further comprises: aplurality of foil supports; a plurality of first flex and tilt supports,each first flex and tilt support supporting one or two of the pluralityof foil supports; a plurality of first pivot supports, each first pivotsupport supporting one of the plurality of first flex and tilt supports;a plurality of second flex and tilt supports, each second flex and tiltsupport supporting two of the plurality of first pivot supports; and aplurality of second pivot supports, each second pivot support supportingone of the plurality of second flex and tilt supports.
 45. The thrustbearing of claim 44 wherein: the plurality of foil supports aregenerally radial; the plurality of first pivot supports are generallyradial; and the plurality of second pivot supports are generally radial.46. The thrust bearing of claim 39 wherein said bearing is hydrodynamic.47. The thrust bearing of claim 39 where said bearing is hydrostatic.